Low working memory relative to other index scores on the WISC can be a flag for a LD. Working memory is the ability to hold information in short term memory, manipulate it and then create output. Poor working memory often impacts writing output since the writer must organize the thoughts, create the sentence and actually put the words down on paper using proper writing conventions, spelling etc. It can also make math computation difficult - for example word problems, multi-step processes such as long division etc. In the higher grades it can sometimes hinder reading comprehension - not because of poor decoding skills or language process skills - but because the reader may "forget" complex information and find it difficult to both "read" and employ active reading strategies to aid comprehension and memory.
That said, it seems like maybe something more is going on. When you had her tested, did the evaluator administer any achievement tests to check on reading levels? How about tests to measure aspects of reading such as phonemic awareness, naming skills (CTOPP, RAN/RAS would be examples).
It sounds like there may be some sort of orthographic processing/ reading issue going on that could be interfering with aspects of written language.
The other issue that relatively low working memory could signal would be attention & concentration difficulties. This could be adhd-inattentive type (not hyperactive). Kids with adHD in attentive are often very calm, well behaved. They often appear that they are very focused and can spend long lengths of time on an activity. These "long lengths" are often an outcome of inattention and inefficiencies, rather than a concentrated effort.
My 16 year old read at age 4 and soared through elementary school. In MS things started becoming very difficult as the complexity and amount of work increased and the amount of structure decreased. Finally in 9th grade we had her tested and found that she has some significant concentration issues and working memory deficits. Her reading fluency was also surprisingly low for a child that loved to read at one time. Basically, she had been able to compensate for all those years, but things became too complex in HS to keep it together without extra help.
She now is tutored once a week to help her prioritize her work and to learn study strategies to overcome her WM deficits. She also gets extra time on tests and copies of class notes since she cannot listen and take notes at the same time.
We were able to put this action in place because we had the testing and recommendations from a neuropsychologist to help us. I think it would be valuable to have your daughter re-tested if possible or to at least look closely at the evaluation from the spring to determine if there were any issues that may have been overlooked.
